The present invention relates to electrical machines and in particular, to electrical machines for use in conjunction with gas turbine engines.
Gas turbine engines, such as aero engines, are required to generate electrical energy for various purposes within and external to the engine, such as to provide power for control systems or to provide electrical power to an airframe. It has been proposed to provide a mechanical link from a rotating component of the engine, to a generator, in order to generate this electrical power. In an attempt to reduce mechanical complexity, it has been further proposed to incorporate an electrical generator within the rotating spools of the engine, preferably the high pressure spool. However, space limitations in the region of the central axis of the engine have been found to be such that this proposal is not wholly satisfactory.
It will be apparent that a device used for electrical generation while the engine is running can be used in reverse to provide drive, such as for starting the engine, and for this reason, the term xe2x80x9celectrical machinexe2x80x9d will be used herein to encompass a device used either as an electrical generator or as an electrical motor.
The present invention provides a gas turbine engine comprising at least one ring of rotating blades, and comprising an electrical machine which has a rotating part and a fixed part, wherein the rotating part is provided by the rotating blade ring.
Preferably, the rotating part is provided by an extremity of the blades. The extremity may be located beyond those parts of the blades which provide the aerodynamic function of the blades. The rotating part may be provided at the radially outward extremity of the blades. The blades are preferably shrouded, the shrouding separating those parts of the blades which provide the aerodynamic function of the blades, from those parts which provide the rotating part. The blades may be shrouded at the radially outer end of those parts which provide the aerodynamic function, and in that the electrical machine is provided substantially wholly outside the shrouded region.
The blades may be unshrouded. The blades may be unshrouded and have parts which provide the aerodynamic function of the blades, the aerodynamic parts further providing a part of the electrical machine.
The fixed part of the machine preferably comprises coils. The rotating part of the machine may comprise magnetically permeable material and/or permanently magnetised material. The parts of the machine preferably operate to form a permanent magnet machine, a transverse flux machine or a switched reluctance machine.
The blades preferably form a compressor or turbine of the engine. The engine may be a multi-shaft engine. The machine may be operable as a generator to draw energy from the engine, and/or a motor to drive the engine, whereby the machine may be used to transfer energy to or from the engine.
The fixed part of the machine may provide at least part of the containment system for the blades.